1. Field of the Invention
This invention relates to the preparation of very finely divided particles, of polypyrrolidone (nylon-4), and to biocidal compositions containing iodine made from them, and specifically to the compound formed by complexing polypyrrolidone with iodine, the latter being broadly referred to as an iodophor.
2. The Prior Art
The complex of nylon-4 and iodine is disclosed in U.S. patent application Ser. No. 933,856 filed Aug. 15, 1978, which is a continuing application of Ser. No. 677,033 filed Apr. 4, 1977, which in turn was a continuing application of Ser. No. 525,845 filed Nov. 21, 1974, and in corresponding foreign patents, e.g., Canadian Patent No. 1,119,748. Among the uses described for this complex is that of an antiseptic and germicidal ointment for topical application where the sustained release of elemental iodine over a period of time will prevent infection of a wound or burn.
It has been suggested that particles prepared by grinding the solid polymer be employed in formulating the ointment. However, the solid polymer is very difficult to grind and conventional comminuting and grinding techniques produce a gritty material not completely suitable for use in ointments, that are intended for topical use on humans. Such powders are not sufficiently finely divided to disperse well in a matrix used for preparing ointments. Further, it is desirable that ointments be prepared from particles which are free of any gritty feel to the touch.
An antiseptic-germicidal ointment made from the iodine complex of polyvinylpyrrolidone, also known as PVP or povidone, has been sold as an over-the-counter preparation for many years. There is, however, an undesirable drawback when using this PVP complex. Polyvinylpyrrolidone is water soluble and accordingly its complex with iodine is water soluble. Because of this solubility the polymer complex can get into the blood stream and while the lower molecular weight components of this polymer may be eliminated by the kidney, the higher molecular weight material is retained and this build-up can cause kidney damage. It is possible to fractionate the polyvinylpyrrolidone used for making the iodine complex to at least partially eliminate the higher molecular weight material which is retained by the kidney. However, this process is not only expensive, but imperfect so that some high molecular weight material is still retained. In addition to the potential adverse physiological effects, the water soluble nature of the PVP iodine complex allows it to be diluted and washed away by perspiration as well as body fluids emanating from the wound, thereby leaving the site without biocidal protection. It is therefore desirable to provide an antiseptic ointment in which the iodine carrier is insoluble in water and therefore incapable of entering the blood stream, and which will not be washed away by exuded body fluids. The polypyrrolidone-iodine complex, unlike polyvinylpyrrolidone, is insoluble in water, as well as other common solvents, and its iodine complex is likewise insoluble.
The complex will form with polypyrrolidone in any physical form, e.g., molded objects, films, fibers, fibrils, particles, etc. For preparing an ointment a very fine particle size is required and heretofore it has not been possible to prepare such a fine material free from a gritty feel and readily dispersable.
The preparation of a complex of iodine with a water insoluble gel forming material for use as a disinfectant has been disclosed in U.S. Pat. No. 4,010,259 issued Mar. 1, 1977. The gel, or gel-forming hydrophilic organic compound is capable of complexing with iodine in an aqueous and/or ethanol solution to form an iodophor, from which iodine can be repeatedly extracted. This iodine carrier is prepared by reacting a polyhydoxyl organic compound, such as starch, polysaccharides or polyvinyl alcohol, with a so-called cross-linking agent that is a bi-functional glycerol derivative, such as epichlorohydrin. The iodophor obtained by this process is described as having utility in its dried particulate form in the preparation of ointments and powders for topical disinfectant use. However, the method of preparing the gel is relatively complex and requires numerous process steps which include prolonged heating, separation and the like, in order to obtain the iodophors.
In contrast, an excellent iodophor may be formed from polypyrrolidone in a few minutes as disclosed in the aforementioned patent application as well as in the issued foreign patents. The only obstacle to its use as an ointment for topical application is t he lack of a suitable non-gritty finely divided form of the polymer.
It is therefore an object of this invention to provide a novel and economical method of forming finely divided particles of polypyrrolidone which are readily dispensable.
It is likewise an object of this invention to provide a method of dispersing the finely divided nylon-4 particles without the formation of agglomerates.
It is also an object of this invention to produce finely divided particles of nylon-4 which are free of a gritty feel and smooth to the touch.
It is a further object of this invention to provide a commercially practical method of forming a relatively uniform, finely divided polymer of 2-pyrrolidone which has industrial utility as, for example, in cosmetic and pharmaceutical applications.
It is another object of this invention to provide a method of forming a complex of polypyrrolidone and iodine in a form suitable for making an ointment for topical application.
It is a still further object of this invention to provide finely divided and dispensable polypyrrolidone-iodine particles which are suitable for preparing iodophors in the form of ointments for human and veterinary use and which are insoluble in the blood stream and therefore cannot cause damage to the kidneys.
Other objects will be apparent from the more detailed description given below.